Capacitor structure having vertical diffusion plates

ABSTRACT

A capacitor structure includes a semiconductor substrate, a first vertical diffusion plate in the semiconductor substrate, a first STI structure in the semiconductor substrate and surrounding the first vertical diffusion plate, a second vertical diffusion plate in the semiconductor substrate and surrounding the first STI structure, and an ion well in the semiconductor substrate. The ion well is disposed directly under the first vertical diffusion plate, the first STI structure and the second vertical diffusion plate. The second vertical diffusion plate is electrically coupled to an anode of the capacitor structure. The first vertical diffusion plate is electrically coupled to a cathode of the capacitor structure.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No. 16/294,944, filed Mar. 7, 2019, which is a continuation of International Application No. PCT/CN2019/073987, filed Jan. 30, 2019, both of which are incorporated herein by reference in their entireties.

BACKGROUND

The present disclosure generally relates to the field of semiconductor technology and, more particularly, to a capacitor structure having vertically-arranged diffusion plates in a silicon substrate.

As known in the art, 3D NAND is a flash memory technology which stacks memory cells vertically to increase capacity for higher storage density and lower cost per gigabyte.

In 3D NAND technology, memory cells are operated at high voltages, and capacitors are required to implement voltage boosting. Typically, MOS capacitors, MOM capacitors, or poly-to-poly capacitors are used in 3D NAND chip circuits.

As 3D NAND technology is moving toward high density and high capacity, especially from 64-layer to 128-layer scheme, the number of devices and the number of traces have increased significantly, while the area of chip has remained essentially unchanged. As a result, the space for silicon wafer and back-end routing is getting smaller and smaller. Conventional MOS capacitors or MOM capacitors usually require a large chip area or metal trace area in the back-end stage, and the large-area MOS capacitor may cause time-dependent dielectric breakdown (TDDB) problems.

Therefore, there is still a need in the art for a novel capacitor structure to meet the circuit requirements, and at the same time, it does not need to occupy too much space.

SUMMARY

It is one object of the present disclosure to provide a capacitor structure having vertically-arranged diffusion plates in a silicon substrate, which is capable of solving the above-mentioned prior art shortcomings and deficiencies.

One aspect of the present disclosure provides a capacitor structure including a semiconductor substrate of a first conductivity type, a first vertical diffusion plate of the first conductivity type disposed in the semiconductor substrate, a first shallow trench isolation (STI) structure disposed in the semiconductor substrate and surrounding the first vertical diffusion plate, a second vertical diffusion plate of the first conductivity type disposed in the semiconductor substrate and surrounding the first STI structure, and an ion well of a second conductivity type disposed in the semiconductor substrate. The ion well is disposed directly under the first vertical diffusion plate, the first STI structure and the second vertical diffusion plate.

According to some embodiments, the first conductivity type is P type and the second conductivity type is N type.

According to some embodiments, the ion well isolates the first vertical diffusion plate from the second vertical diffusion plate.

According to some embodiments, the first vertical diffusion plate is electrically coupled to a first voltage and the second vertical diffusion plate is electrically coupled to a second voltage, wherein the second voltage is higher than the first voltage.

According to some embodiments, a capacitor is formed between the first vertical diffusion plate and the second vertical diffusion plate with the first STI structure interposed therebetween acting as a capacitor dielectric layer.

According to some embodiments, the capacitor structure further comprises a first heavily doped region of the first conductivity type disposed at a surface of the first vertical diffusion plate, and a second heavily doped region of the first conductivity type disposed at a surface of the second vertical diffusion plate.

According to some embodiments, the capacitor structure further comprises a second shallow trench isolation (STI) structure disposed in the semiconductor substrate and the second STI structure surrounding the second vertical diffusion plate, the first STI structure, and the first vertical diffusion plate.

According to some embodiments, the second STI structure, the second vertical diffusion plate, the first STI structure are arranged concentrically with the first vertical diffusion plate.

According to some embodiments, the first vertical diffusion plate and the second vertical diffusion plate are silicon active areas defined and isolated by the first STI structure and the second STI structure.

According to some embodiments, the capacitor structure further comprises a passive element directly on a top surface of the first STI structure or the second STI structure.

According to some embodiments, the passive element comprises a resistor. According to some embodiments, the passive element comprises polysilicon.

According to some embodiments, the capacitor structure further comprises a third vertical diffusion plate surrounding the second STI structure, the second vertical diffusion plate, the first STI structure, and the first vertical diffusion plate; and a third shallow trench isolation (STI) structure surrounding the third vertical diffusion plate, the second STI structure, the second vertical diffusion plate, the first STI structure, and the first vertical diffusion plate.

According to some embodiments, the capacitor structure further comprises a fourth vertical diffusion plate surrounding the third STI structure, the third vertical diffusion plate, the second STI structure, the second vertical diffusion plate, the first STI structure, and the first vertical diffusion plate; and a fourth shallow trench isolation (STI) structure surrounding the fourth vertical diffusion plate, the third STI structure, the third vertical diffusion plate, the second STI structure, the second vertical diffusion plate, the first STI structure, and the first vertical diffusion plate.

According to some embodiments, the second vertical diffusion plate, the fourth vertical diffusion plate and the ion well are electrically coupled to an anode, and the first vertical diffusion plate and the third vertical diffusion plate are electrically coupled to a cathode.

According to some embodiments, the ion well comprises annular vertical portion surrounding the fourth STI structure.

According to some embodiments, the semiconductor substrate is a silicon substrate.

Another aspect of the present disclosure provides a capacitor structure including a semiconductor substrate of a first conductivity type, a first vertical diffusion plate of the first conductivity type disposed in the semiconductor substrate, a first shallow trench isolation (STI) structure disposed in the semiconductor substrate and surrounding the first vertical diffusion plate, a second vertical diffusion plate of the first conductivity type disposed in the semiconductor substrate and surrounding the first STI structure, and an ion well of a second conductivity type disposed in the semiconductor substrate. The ion well is disposed directly under the first vertical diffusion plate, the first STI structure and the second vertical diffusion plate. The second vertical diffusion plate is electrically coupled to an anode of the capacitor structure. The first vertical diffusion plate is electrically coupled to a cathode of the capacitor structure.

According to some embodiments, the capacitor structure further comprises a second shallow trench isolation (STI) structure disposed in the semiconductor substrate and the second STI structure surrounding the second vertical diffusion plate, the first STI structure, and the first vertical diffusion plate.

According to some embodiments, the second STI structure, the second vertical diffusion plate, the first STI structure are arranged concentrically with the first vertical diffusion plate.

These and other objectives of the present disclosure will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated herein and form a part of the specification, illustrate embodiments of the present disclosure and, together with the description, further serve to explain the principles of the present disclosure and to enable a person skilled in the pertinent art to make and use the present disclosure.

FIG. 1 is a schematic diagram showing an exemplary layout structure of a capacitor structure fabricated in a semiconductor substrate according to one embodiment of the disclosure.

FIG. 2 is a schematic, cross-sectional view taken along line I-I′ in FIG. 1.

FIG. 3 to FIG. 5 are schematic, cross-sectional diagrams showing an exemplary method for fabricating a capacitor structure according to another embodiment of the present disclosure.

Embodiments of the present disclosure will be described with reference to the accompanying drawings.

DETAILED DESCRIPTION

Reference will now be made in detail to exemplary embodiments of the present disclosure, which are illustrated in the accompanying drawings in order to understand and implement the present disclosure and to realize the technical effect. It can be understood that the following description has been made only by way of example, but not to limit the present disclosure. Various embodiments of the present disclosure and various features in the embodiments that are not conflicted with each other can be combined and rearranged in various ways. Without departing from the spirit and scope of the present disclosure, modifications, equivalents, or improvements to the present disclosure are understandable to those skilled in the art and are intended to be encompassed within the scope of the present disclosure.

It is noted that references in the specification to “one embodiment,” “an embodiment,” “an example embodiment,” “some embodiments,” etc., indicate that the embodiment described may include a particular feature, structure, or characteristic, but every embodiment may not necessarily include the particular feature, structure, or characteristic. Moreover, such phrases do not necessarily refer to the same embodiment.

Further, when a particular feature, structure or characteristic is described in contact with an embodiment, it would be within the knowledge of a person skilled in the pertinent art to affect such feature, structure or characteristic in contact with other embodiments whether or not explicitly described.

In general, terminology may be understood at least in part from usage in context. For example, the term “one or more” as used herein, depending at least in part upon context, may be used to describe any feature, structure, or characteristic in a singular sense or may be used to describe combinations of features, structures or characteristics in a plural sense. Similarly, terms, such as “a,” “an,” or “the,” again, may be understood to convey a singular usage or to convey a plural usage, depending at least in part upon context.

It should be readily understood that the meaning of “on,” “above,” and “over” in the present disclosure should be interpreted in the broadest manner such that “on” not only means “directly on” something but also includes the meaning of “on” something with an intermediate feature or a layer therebetween, and that “above” or “over” not only means the meaning of “above” or “over” something but can also include the meaning it is “above” or “over” something with no intermediate feature or layer therebetween (i.e., directly on something).

Further, spatially relative terms, such as “beneath,” “below,” “lower,” “above,” “upper,” and the like, may be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures.

The spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. The apparatus may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein may likewise be interpreted accordingly.

As used herein, the term “substrate” refers to a material onto which subsequent material layers are added. The substrate itself can be patterned. Materials added on top of the substrate can be patterned or can remain unpatterned. Furthermore, the substrate can include a wide array of semiconductor materials, such as silicon, germanium, gallium arsenide, indium phosphide, etc. Alternatively, the substrate can be made from an electrically non-conductive material, such as a glass, a plastic, or a sapphire wafer.

As used herein, the term “layer” refers to a material portion including a region with a thickness. A layer can extend over the entirety of an underlying or overlying structure, or may have an extent less than the extent of an underlying or overlying structure. Further, a layer can be a region of a homogeneous or inhomogeneous continuous structure that has a thickness less than the thickness of the continuous structure. For example, a layer can be located between any pair of horizontal planes between, or at, a top surface and a bottom surface of the continuous structure. A layer can extend horizontally, vertically, and/or along a tapered surface. A substrate can be a layer, can include one or more layers therein, and/or can have one or more layer thereupon, thereabove, and/or therebelow. A layer can include multiple layers. For example, an interconnect layer can include one or more conductor and contact layers (in which contacts, interconnect lines, and/or through holes are formed) and one or more dielectric layers.

As used herein, the term “nominal/nominally” refers to a desired, or target, value of a characteristic or parameter for a component or a process operation, set during the design phase of a product or a process, together with a range of values above and/or below the desired value. The range of values can be due to slight variations in manufacturing processes or tolerances. As used herein, the term “about” indicates the value of a given quantity that can vary based on a particular technology node associated with the subject semiconductor device. Based on the particular technology node, the term “about” can indicate a value of a given quantity that varies within, for example, 10-30% of the value (e.g., ±10%, ±20%, or ±30% of the value).

The present disclosure pertains to a capacitor structure having vertically-arranged diffusion plates in a silicon substrate. The aforesaid capacitor structure may be fabricated on a CMOS wafer, which may be bonded to an array wafer to form a three-dimensional (3D) NAND device. Shallow trench isolation (STI) structures, which function as capacitor dielectric layers, are disposed between the vertically-arranged diffusion plates of the capacitor structure. At the bottom and along the perimeter of the capacitor structure, an N well is disposed in the silicon substrate to electrically isolate the diffusion plates of opposite polarities from one another. The aforesaid capacitor structure may be integrated in a polysilicon gate (poly-gate) capacitor/resistor area so that the space of the CMOS wafer may be efficiently used and the capacitance per unit area may be increased.

Please refer to FIG. 1 and FIG. 2. FIG. 1 is a schematic diagram showing an exemplary layout structure of a capacitor structure fabricated in a semiconductor substrate according to one embodiment of the present disclosure. FIG. 2 is a schematic, cross-sectional view taken along line I-I′ in FIG. 1. It is to be understood that the shapes of the elements or layouts of the capacitor structure depicted through the figures are for illustration purposes only. Different shapes or layouts may be employed according to various embodiments of the present disclosure.

As shown in FIG. 1 and FIG. 2, a capacitor structure 1 may be constructed within a poly-gate capacitor/resistor area (P2 area) in a semiconductor substrate 100 of a semiconductor material such as silicon, but is not limited thereto. According to one embodiment of the present disclosure, the semiconductor substrate 100 may be a P type silicon substrate. However, it is to be understood that other semiconductor substrates such as silicon-on-insulator (SOI) substrates or epitaxial substrates may be employed according to other embodiments.

On the P type silicon substrate, a plurality of CMOS circuit elements (not shown) may be fabricated so as to form a CMOS wafer. The CMOS wafer may be bonded to an array wafer (or memory cell wafer) to form a three-dimensional (3D) NAND device. The capacitor structure 1 of the present disclosure can provide high capacitance that is required to implement voltage boosting during the operation of the 3D NAND device. Further, the capacitor structure 1 of the present disclosure is compatible with current CMOS processes. The capacitor structure 1 of the present disclosure is an integrated capacitor structure that is integrally fabricated with the CMOS circuit elements.

In the non-limiting embodiment illustrated in FIG. 1 and FIG. 2, the capacitor structure 1 comprises a first vertical diffusion plate 110 surrounded by a first shallow trench isolation (STI) structure 104. When viewed from the above, as can be seen in FIG. 1, the first vertical diffusion plate 110 may have a rectangular shape with its longer axis or longer side extending along the reference x-axis and its shorter side extending along the reference y-axis. The first STI structure 104 is a ring-shaped trench isolation that electrically isolates the first vertical diffusion plate 110. It is understood that different shapes or layouts of the first vertical diffusion plate 110 and the first STI structure 104 may be employed according to various embodiments of the present disclosure.

According to one embodiment of the present disclosure, the first vertical diffusion plate 110 is a silicon active area defined and isolated by the first STI structure 104. According to one embodiment of the present disclosure, the first vertical diffusion plate 110 is P-type doped. For example, by performing ion well implantation processes using suitable hard mask, which are commonly performed to form ion wells in the CMOS logic circuit regions, P-type dopants such boron or the like may be implanted into the silicon active area defined and isolated by the first STI structure 104, thereby forming the first vertical diffusion plate 110. A heavily P-type doped region (P⁺ region) 111 may be formed at the surface of the first vertical diffusion plate 110. Therefore, the doping concentration of the first vertical diffusion plate 110 after the ion well implantation processes is higher than that of the semiconductor substrate 100.

According to one embodiment of the present disclosure, for example, the first STI structure 104 may be formed by performing the following steps including but not limited to: (1) etching an annular isolation trench into the semiconductor substrate 100; (2) forming a liner layer such as a silicon oxide or silicon nitride liner on the interior surface of the annular isolation trench; (3) filling the annular isolation trench with a trench-fill insulating layer such as silicon dioxide or HDPCVD oxide; and (4) performing a chemical mechanical polishing (CMP) to remove excess trench-fill insulating layer outside the annular isolation trench.

The capacitor structure 1 further comprises a second vertical diffusion plate 210 surrounding the first STI structure 104 and the first vertical diffusion plate 110. When viewed from the above, as can be seen in FIG. 1, the second vertical diffusion plate 210 is an annular shaped ring that encircles the annular first STI structure 104. The second vertical diffusion plate 210 is defined and isolated by the first STI structure 104 and a second STI structure 105. The second STI structure 105 is also a ring-shaped trench isolation that electrically isolates the second vertical diffusion plate 210. The second STI structure 105 may be formed by the STI process steps as previously described.

According to one embodiment of the present disclosure, the second vertical diffusion plate 210 is a silicon active area defined and isolated by the first STI structure 104 and the second STI structure 105. According to one embodiment of the present disclosure, likewise, the second vertical diffusion plate 210 is P-type doped. For example, by performing ion well implantation processes using suitable hard mask, which are commonly performed to form ion wells in the CMOS logic circuit regions, P-type dopants such boron or the like may be implanted into the silicon active area defined and isolated by the first STI structure 104 and the second STI structure 105, thereby forming the first vertical diffusion plate 110 and the second vertical diffusion plate 210. A heavily P-type doped region (P⁺ region) 211 may be formed at the surface of the second vertical diffusion plate 210.

According to one embodiment of the present disclosure, as can be seen in FIG. 2, a capacitor C₁ (Si-to-Si capacitor) may be formed between the first vertical diffusion plate 110 and the second vertical diffusion plate 210 with the annular first STI structure 104 interposed therebetween acting as a capacitor dielectric layer. A plurality of first contact elements CT₁ may be disposed on the first vertical diffusion plate 110. Through the plurality of first contact elements CT₁ and the metal interconnect 410, the first vertical diffusion plate 110 may be electrically coupled to a cathode of the capacitor structure 1, which is provided with a first voltage. A plurality of second contact elements CT₃ may be disposed on the second vertical diffusion plate 210. Through the plurality of second contact elements CT₂ and the metal interconnect 420, the second vertical diffusion plate 210 may be electrically coupled to an anode of the capacitor structure 1, which is provided with a second voltage. According to one embodiment of the present disclosure, the second voltage is higher than the first voltage.

According to one embodiment of the present disclosure, an N well 101 such as a high-voltage N well (HVNW) is provided at the bottom of the capacitor structure 1 to isolate the first vertical diffusion plate 110 and the second vertical diffusion plate 210 from each other. According to one embodiment of the present disclosure, the N well 101 formed in the semiconductor substrate 100 may be electrically coupled to the anode of the capacitor structure 1 (or the second voltage), thereby forming a reverse-biased PN junction 113 between the N well 101 and the bottom of the first vertical diffusion plate 110 and a reverse-biased PN junction 213 between the N well 101 and the bottom of the second vertical diffusion plate 210. The N well 101 can provide isolation and prevent interference between the capacitor structure 1 and the adjacent circuit elements.

According to one embodiment of the present disclosure, the reverse-biased PN junction 113 and the reverse-biased PN junction 213 may be approximately leveled with a bottom surface of the annular first STI structure 104 and a bottom surface of the second STI structure 105, but is not limited thereto.

According to one embodiment of the present disclosure, passive elements 302 and 304 such as resistors or the like may be formed on the top surface of the first STI structure 104 and passive elements 306 such as resistors or the like may be formed on the top surface of the second STI structure 105. According to one embodiment of the present disclosure, the passive elements 302, 304, and 306 may be composed of polysilicon, but is not limited thereto. According to one embodiment of the present disclosure, the passive elements 302, 304, and 306 are only formed on the first STI structure 104 and the second STI structure 105, respectively. It is understood that the layout and number of the passive elements 302, 304, and 306 illustrated in FIG. 1 is for illustration purposes only.

According to one embodiment of the present disclosure, the capacitor structure 1 may further comprises a third vertical diffusion plate 120 surrounding the second STI structure 105, the second vertical diffusion plate 210, the first STI structure 104, and the first vertical diffusion plate 110. When viewed from the above, as can be seen in FIG. 1, the third vertical diffusion plate 120 is an annular shaped ring that encircles the annular second STI structure 105. The third vertical diffusion plate 120 is defined and isolated by the second STI structure 105 and a third STI structure 106. The third STI structure 106 is also a ring-shaped trench isolation that electrically isolates the third vertical diffusion plate 120. The third STI structure 106 may be formed by the STI process steps as previously described. According to one embodiment of the present disclosure, the third STI structure 106, the third vertical diffusion plate 120, the second STI structure 105, the second vertical diffusion plate 210, and the first STI structure 104 are arranged concentrically with the innermost first vertical diffusion plate 110.

According to one embodiment of the present disclosure, the third vertical diffusion plate 120 is a silicon active area defined and isolated by the second STI structure 105 and the third STI structure 106. According to one embodiment of the present disclosure, likewise, the third vertical diffusion plate 120 is P-type doped. For example, by performing ion well implantation processes using suitable hard mask, which are commonly performed to form ion wells in the CMOS logic circuit regions, P-type dopants such boron or the like may be implanted into the silicon active area defined and isolated by the second STI structure 105 and the third STI structure 106, thereby forming the first vertical diffusion plate 110, the second vertical diffusion plate 210, and the third vertical diffusion plate 120. A heavily P-type doped region (P⁺ region) 121 may be formed at the surface of the third vertical diffusion plate 120.

According to one embodiment of the present disclosure, as can be seen in FIG. 2, a capacitor C₂ (Si-to-Si capacitor) may be formed between the second vertical diffusion plate 210 and the third vertical diffusion plate 120 with the annular second STI structure 105 interposed therebetween acting as a capacitor dielectric layer. A plurality of third contact elements CT₃ may be disposed on the third vertical diffusion plate 120. Through the plurality of third contact elements CT₃ and the metal interconnect 410, the third vertical diffusion plate 120 may be electrically coupled to the cathode of the capacitor structure 1, which is provided with the first voltage. Therefore, according to one embodiment of the present disclosure, as can be seen in FIG. 2, the first vertical diffusion plate 110 and the third vertical diffusion plate 120 are both electrically coupled to the cathode.

According to one embodiment of the present disclosure, passive elements 308 such as resistors or the like may be formed on the top surface of the third STI structure 106. According to one embodiment of the present disclosure, the passive elements 308 may be composed of polysilicon, but is not limited thereto. According to one embodiment of the present disclosure, the passive elements 308 are only formed on the third STI structure 106. It is understood that the layout and number of the passive elements 308 illustrated in FIG. 1 is for illustration purposes only.

According to one embodiment of the present disclosure, the capacitor structure 1 may further comprises a fourth vertical diffusion plate 220 surrounding the third STI structure 106, the third vertical diffusion plate 120, the second STI structure 105, the second vertical diffusion plate 210, the first STI structure 104, and the first vertical diffusion plate 110. When viewed from the above, as can be seen in FIG. 1, the fourth vertical diffusion plate 220 is an annular shaped ring that encircles the annular third STI structure 106. The fourth vertical diffusion plate 220 is defined and isolated by the third STI structure 106 and a fourth STI structure 107. The fourth STI structure 107 is also a ring-shaped trench isolation that electrically isolates the fourth vertical diffusion plate 220. The fourth STI structure 107 may be formed by the STI process steps as previously described. According to one embodiment of the present disclosure, the fourth STI structure 107, the fourth vertical diffusion plate 220, the third STI structure 106, the third vertical diffusion plate 120, the second STI structure 105, the second vertical diffusion plate 210, and the first STI structure 104 are arranged concentrically with the innermost first vertical diffusion plate 110.

According to one embodiment of the present disclosure, the fourth vertical diffusion plate 220 is a silicon active area defined and isolated by the third STI structure 106 and the fourth STI structure 107. According to one embodiment of the present disclosure, likewise, the fourth vertical diffusion plate 220 is P-type doped. For example, by performing ion well implantation processes using suitable hard mask, which are commonly performed to form ion wells in the CMOS logic circuit regions, P-type dopants such boron or the like may be implanted into the silicon active area defined and isolated by the third STI structure 106 and the fourth STI structure 107, thereby forming the first vertical diffusion plate 110, the second vertical diffusion plate 210, the third vertical diffusion plate 120, and the fourth vertical diffusion plate 220. A heavily P-type doped region (P⁺ region) 221 may be formed at the surface of the fourth vertical diffusion plate 220.

According to one embodiment of the present disclosure, as can be seen in FIG. 2, a capacitor C₃ (Si-to-Si capacitor) may be formed between the third vertical diffusion plate 120 and the fourth vertical diffusion plate 220 with the annular third STI structure 106 interposed therebetween acting as a capacitor dielectric layer. A plurality of fourth contact elements CT₄ may be disposed on the fourth vertical diffusion plate 220. Through the plurality of fourth contact elements CT₄ and the metal interconnect 420, the fourth vertical diffusion plate 220 may be electrically coupled to the anode of the capacitor structure 1, which is provided with the second voltage. Therefore, according to one embodiment of the present disclosure, as can be seen in FIG. 2, the second vertical diffusion plate 210 and the fourth vertical diffusion plate 220 are both electrically coupled to the anode.

According to one embodiment of the present disclosure, passive elements 310 such as resistors or the like may be formed on the top surface of the fourth STI structure 107. According to one embodiment of the present disclosure, the passive elements 310 may be composed of polysilicon, but is not limited thereto. According to one embodiment of the present disclosure, the passive elements 310 are only formed on the fourth STI structure 107. It is understood that the layout and number of the passive elements 310 illustrated in FIG. 1 is for illustration purposes only.

According to one embodiment of the present disclosure, the N well 101 comprises an annular vertical portion 101 a surrounding the fourth STI structure 107. A heavily P-type doped region (P⁺ region) 102 may be formed at the surface of the annular vertical portion 101 a. A plurality of fifth contact elements CT₅ may be disposed on the annular vertical portion 101 a. Through the plurality of fifth contact elements CT₅ and the metal interconnect 420, the N well 101 may be electrically coupled to the anode of the capacitor structure 1, which is provided with the second voltage.

Structurally, the capacitor structure 1 includes a semiconductor substrate 100 of a first conductivity type, a first vertical diffusion plate 110 of the first conductivity type disposed in the semiconductor substrate 100, a first shallow trench isolation (STI) structure 104 disposed in the semiconductor substrate 100 and surrounding the first vertical diffusion plate 110, a second vertical diffusion plate 210 of the first conductivity type disposed in the semiconductor substrate 100 and surrounding the first STI structure 104, and an ion well 101 of a second conductivity type disposed in the semiconductor substrate 100. The ion well 101 is disposed directly under the first vertical diffusion plate 110, the first STI structure 104 and the second vertical diffusion plate 210.

According to some embodiments, the first conductivity type is P type and the second conductivity type is N type.

According to some embodiments, the ion well 101 isolates the first vertical diffusion plate 110 from the second vertical diffusion plate 210.

According to some embodiments, the first vertical diffusion plate 110 is electrically coupled to a first voltage and the second vertical diffusion plate 210 is electrically coupled to a second voltage, wherein the second voltage is higher than the first voltage.

According to some embodiments, a capacitor C₁ is formed between the first vertical diffusion plate 110 and the second vertical diffusion plate 210 with the first STI structure 104 interposed therebetween acting as a capacitor dielectric layer.

According to some embodiments, the capacitor structure 1 further comprises a first heavily doped region 111 of the first conductivity type disposed at a surface of the first vertical diffusion plate 110, and a second heavily doped region 211 of the first conductivity type disposed at a surface of the second vertical diffusion plate 210.

According to some embodiments, the capacitor structure 1 further comprises a second shallow trench isolation (STI) structure 105 disposed in the semiconductor substrate 100. The second STI structure 105 surrounds the second vertical diffusion plate 210, the first STI structure 104, and the first vertical diffusion plate 110.

According to some embodiments, the second STI structure 105, the second vertical diffusion plate 210, the first STI structure 104 are arranged concentrically with the first vertical diffusion plate 110.

According to some embodiments, the first vertical diffusion plate 110 and the second vertical diffusion plate 210 are silicon active areas defined and isolated by the first STI structure 104 and the second STI structure 105.

According to some embodiments, the capacitor structure 1 further comprises a passive element 302, 306 directly on a top surface of the first STI structure 104 or the second STI structure 105.

According to some embodiments, the passive element 302, 306 comprises a resistor. According to some embodiments, the passive element 302, 306 comprises polysilicon.

According to some embodiments, the capacitor structure further comprises a third vertical diffusion plate 120 surrounding the second STI structure 105, the second vertical diffusion plate 210, the first STI structure 104, and the first vertical diffusion plate 110, and a third shallow trench isolation (STI) structure 106 surrounding the third vertical diffusion plate 120, the second STI structure 105, the second vertical diffusion plate 210, the first STI structure 104, and the first vertical diffusion plate 110.

According to some embodiments, the capacitor structure 1 further comprises a fourth vertical diffusion plate 220 surrounding the third STI structure 106, the third vertical diffusion plate 120, the second STI structure 105, the second vertical diffusion plate 210, the first STI structure 104, and the first vertical diffusion plate 110, and a fourth shallow trench isolation (STI) structure 107 surrounding the fourth vertical diffusion plate 220, the third STI structure 106, the third vertical diffusion plate 120, the second STI structure 105, the second vertical diffusion plate 210, the first STI structure 104, and the first vertical diffusion plate 110.

According to some embodiments, the second vertical diffusion plate 210, the fourth vertical diffusion plate 220 and the ion well 101 are electrically coupled to an anode, and the first vertical diffusion plate 110 and the third vertical diffusion plate 120 are electrically coupled to a cathode.

According to some embodiments, the ion well 101 comprises annular vertical portion 101 a surrounding the fourth STI structure 107.

According to some embodiments, the semiconductor substrate 100 is a silicon substrate.

Please refer to FIG. 3 to FIG. 5. FIG. 3 to FIG. 5 are schematic, cross-sectional diagrams showing an exemplary method for fabricating a capacitor structure according to another embodiment of the present disclosure, wherein like regions, layers, or elements are designated by like numeral numbers.

As shown in FIG. 3, the P2 area of the semiconductor substrate 100 such as a P-type silicon substrate is subjected to STI processes as previously described, thereby forming concentric rings of active areas and STI structures including, for example, the first vertical diffusion plate 110 surrounded by the first STI structure 104, the second vertical diffusion plate 210, the second STI structure 105, the third vertical diffusion plate 120, the third STI structure 106, the fourth vertical diffusion plate 220, and the fourth STI structure 107. Patterned polysilicon layers are formed on the STI structures. The patterned polysilicon layers may form passive elements such as the passive elements 302-310.

As shown in FIG. 4, subsequently, the P2 area of the semiconductor substrate 100 is subjected to an ion well implantation such as high-voltage N well implantation. For example, N type dopants such as phosphorus or arsenic are implanted into the semiconductor substrate 100, thereby forming an N well 101. The P2 area of the semiconductor substrate 100 is also subjected to several ion implantation processes to form P-type doped first vertical diffusion plate 110, P-type doped second vertical diffusion plate 210, P-type doped third vertical diffusion plate 120, P-type doped fourth vertical diffusion plate 220, P⁺ regions 111, 121, 211, 221, and N⁺ region 102.

As shown in FIG. 5, dielectric layers (not shown) are deposited on the semiconductor substrate 100. Subsequently, contact elements CT₁˜CT₅ are formed on the P⁺ regions 111, 121, 211, 221, and N⁺ region 102, respectively. Metal interconnects 410 and 420 are then formed on the semiconductor substrate 100 by performing CMOS back-end of line processes. According to some embodiments, the second vertical diffusion plate 210, the fourth vertical diffusion plate 220 and the ion well 101 are electrically coupled to an anode node (relatively higher voltage), and the first vertical diffusion plate 110 and the third vertical diffusion plate 120 are electrically coupled to a cathode node (relatively lower voltage). By providing such configuration, reverse-biased PN junctions 113, 213 may be formed between the P-type doped vertical diffusion plates and the N well 101, thereby improving the isolation of the capacitor structure.

Those skilled in the art will readily observe that numerous modifications and alterations of the device and method may be made while retaining the teachings of the present disclosure. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims. 

What is claimed is:
 1. A capacitor structure, comprising: a semiconductor substrate of a first conductivity type; a first vertical diffusion plate of the first conductivity type disposed in the semiconductor substrate; a first shallow trench isolation (STI) structure disposed in the semiconductor substrate and the first STI structure surrounding the first vertical diffusion plate; a second vertical diffusion plate of the first conductivity type disposed in the semiconductor substrate and the second vertical diffusion plate surrounding the first STI structure; and an ion well of a second conductivity type disposed in the semiconductor substrate, wherein the ion well is disposed directly under the first vertical diffusion plate, the first STI structure and the second vertical diffusion plate. 